The ABINIT Users Mailing List ( CLOSED )

[Prasenjit Sen <prasen@mri.ernet.in>]

Dear ABINIT users,
     I am trying to do a finite temp. MD calculation in a Si surface
system. From the ouput of a small run, I have the following questions, Any
help would be very useful.

1. Should I use nsym=1 for finite T MD calculations? The default seems to
give errors because the symmetry finder cannot find symmetry related atoms
after 1 or 2 MD steps.

2. Is the effective temp. of the system printed out somewhere after every
MD step? It does say "converged velocities for T=... Ha" after every step,
but this value of T remains constant and is *exactly* equal to the input
temp. It seems unlikely that this is the actual temp. of the
system. One does expect some fluctuations for a finite system. It prints an
"Effective temperature" only at the beginning of the calculation.

3. In *a few* MOLDYN steps, the SCF cycle does not converge within the
allowed number of steps. In fact, in these cases, the total energy
oscillates between two values, and there does not seem any tendency of
convergence of the SCF cycle. Has anybody else come across such behavior
for any other system?

4. How do I realise if I am using the right number for the Nose' mass (the
parameter noseinsert)?

     Thanks in advance for any help.

   Sincerely,
   Prasenjit Sen

P.S. I am enclosing my input file below

 =======================================================================
  Harish-Chandra Research Institute     Phone: +91-532-2667509 Extn. 2007
  Chhatnag Road, Jhunsi                  Or    +91-532-2667511*2007
  Allahabad, UP 211019
       INDIA                            Fax:   +91-532-2568036
 =======================================================================
==== basic input variables ===
acell   3.818400000   3.818400000   15.269900000   angstrom
chkprim  0
diecut   2.3
diemac   12.0
diemix    0.5
ecut   450.0 eV
iprcel   45
iscf  3
ixc   1
kptopt   1
natom   28
nband   55
nline   5
kptrlatt
        2  0  0
        0  2  0
        0  0  1
nstep   60
shiftk
       0.500  0.500  0.000
ntypat   2
occopt   1
rprim
       2.0000000000000000    0.0000000000000000    0.0000000000000000
       0.0000000000000000    2.0000000000000000    0.0000000000000000
       0.0000000000000000    0.0000000000000000    1.0000000000000000
toldff  5.0d-6
typat   20*1  8*2
xred
              0.0000000000E+00  1.5996995304E-01  3.7126247555E-01
              0.0000000000E+00  4.4379593651E-01  4.1979580693E-01
              5.0000000000E-01  1.5996995304E-01  3.7126247555E-01
              5.0000000000E-01  4.4379593651E-01  4.1979580693E-01
              2.5000000000E-01  1.3922297530E-02  3.2293877643E-01
              2.5000000000E-01  4.8813582203E-01  3.2805145313E-01
              7.5000000000E-01  1.3922297530E-02  3.2293877643E-01
              7.5000000000E-01  4.8813582203E-01  3.2805145313E-01
              2.5000000000E-01  2.6105290841E-01  2.2538172919E-01
              2.5000000000E-01  7.4766515713E-01  2.4170413180E-01
              7.5000000000E-01  2.6105290841E-01  2.2538172919E-01
              7.5000000000E-01  7.4766515713E-01  2.4170413180E-01
              0.0000000000E+00  2.4979029122E-01  1.3886883731E-01
              0.0000000000E+00  7.5069430588E-01  1.4950521475E-01
              5.0000000000E-01  2.4979029122E-01  1.3886883731E-01
              5.0000000000E-01  7.5069430588E-01  1.4950521475E-01
              0.0000000000E+00  0.0000000000E+00  5.6968284010E-02
              0.0000000000E+00  5.0000000000E-01  5.6968284010E-02
              5.0000000000E-01  0.0000000000E+00  5.6968284010E-02
              5.0000000000E-01  5.0000000000E-01  5.6968284010E-02
             -1.5055385507E-01 -1.1738360888E-02 -3.5839766227E-03
              1.5055385507E-01 -1.1738360888E-02 -3.5839766227E-03
             -1.5043461137E-01  5.1252747451E-01 -3.6714917881E-03
              1.5043461137E-01  5.1252747451E-01 -3.6714917881E-03
              3.4944614493E-01 -1.1738360888E-02 -3.5839766227E-03
              6.5055385507E-01 -1.1738360888E-02 -3.5839766227E-03
              3.4956538863E-01  5.1252747451E-01 -3.6714917881E-03
              6.5043461137E-01  5.1252747451E-01 -3.6714917881E-03
zatnum   14.0   1.0

=== geometry optimization variables ===
#amu use defaults
dtion    100
ionmov   8
mditemp  700
noseinsert  1.0d5
nsym     1
ntime    50